Though weight-loss programs amount to a $2.5-billion-a-year industry in the U.S., very few of them can be proven effective, according to a new Johns Hopkins study.
In a review of 32 major commercial weight-loss programs in the U.S., researchers from the JHU School of Medicine found that only two—Weight Watchers and Jenny Craig—are backed by reliable data showing sustained weight loss. Other programs such as NutriSystem and the Atkins diet show promising results, but more studies are needed to look at long-term outcomes, the report suggests.
The findings, published in the April 6 issue of the Annals of Internal Medicine, are intended to help physicians guide overweight and obese patients.
"Entering any weight-loss program, people come in with idea of losing large amounts of weight," Kimberly Gudzune an assistant professor of medicine and a weight-loss specialist at the School of Medicine, told Vox. "It's not impossible to do, but it's the more unusual occurrence."
To arrive at their conclusions, Hopkins researchers reviewed 4,200 studies of the 32 major weight-loss programs. They found that only 11 of the programs met the scientific "gold standard" for reliability in the studies—using randomized clinical trials.
Within that narrow group, only Weight Watchers and Jenny Craig are backed by data proving that participants, on average, lost more weight after one year than dieters using their own plans and/or other resources. The results in those programs were generally modest, with Weight Watchers participants averaging 2.6 percent more weight loss than the other dieters, and Jenny Craig participants averaging 4.9 percent more weight loss.
Importantly, both Weight Watchers and Jenny Craig are supported by clinical trials lasting more than 12 months. Study co-author Jeanne Clark, JHU professor of Medicine and director of the Division of General Internal Medicine, notes the value of following such results for more than a year. The benefits of weight loss—including lower blood pressure, cholesterol, and blood sugar, along with decreased risk of diseases like diabetes—are "long-term goals," Clark said. "Losing weight for three months, then regaining it, has limited health benefits."
Researchers also found that programs based on the Atkins diet—high in fat, low in carbohydrates—showed modest "promising" results at six and 12 months. NutriSystem produced weight-loss at three months, but long-term trials weren't available. Meanwhile, programs based on very-low-calorie meal replacement (such as MediFast) showed weight-loss results up to six months, but not much evidence beyond that.Read more from Hopkins Medicine